RW, WRW, and WIS all produce biased (nonuniform) node samples.
But their bias is known and therefore can be corrected by an appropriate re-weighting of the measured values.
This can be done using the Hansen-Hurwitz estimator [1]} as first shown in [2]}, [3]} for random walks and also used in [4]}.
Let every node \(v\in V\)  carry a value \(x(v)\) . We can estimate the population total \(x_{\scriptscriptstyle \textrm {tot}} = \sum _v x(v)\)  by
\(\hat{x}_{\scriptscriptstyle \textrm {tot}} = \frac{1}{n}\sum _{v\in S} \frac{x(v)}{\pi (v)},\) 
